nsz Git - libfirm/blob - ir/ana/irconsconfirm.c

   1 /*
   2  * Copyright (C) 1995-2008 University of Karlsruhe.  All right reserved.
   3  *
   4  * This file is part of libFirm.
   5  *
   6  * This file may be distributed and/or modified under the terms of the
   7  * GNU General Public License version 2 as published by the Free Software
   8  * Foundation and appearing in the file LICENSE.GPL included in the
   9  * packaging of this file.
  10  *
  11  * Licensees holding valid libFirm Professional Edition licenses may use
  12  * this file in accordance with the libFirm Commercial License.
  13  * Agreement provided with the Software.
  14  *
  15  * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
  16  * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  17  * PURPOSE.
  18  */
  19
  20 /**
  21  * @file
  22  * @brief    Construction of Confirm nodes
  23  * @author   Michael Beck
  24  * @date     6.2005
  25  */
  26 #include "config.h"
  27
  28 #include "irconsconfirm.h"
  29
  30 #include "irgraph_t.h"
  31 #include "irnode_t.h"
  32 #include "ircons_t.h"
  33 #include "irgmod.h"
  34 #include "iropt_dbg.h"
  35 #include "iredges_t.h"
  36 #include "irgwalk.h"
  37 #include "irprintf.h"
  38 #include "irgopt.h"
  39 #include "irpass.h"
  40 #include "irtools.h"
  41 #include "array_t.h"
  42 #include "debug.h"
  43 #include "error.h"
  44 #include "irflag.h"
  45
  46 /**
  47  * Walker environment.
  48  */
  49 typedef struct env_t {
  50         unsigned num_confirms;  /**< Number of inserted Confirm nodes. */
  51         unsigned num_consts;    /**< Number of constants placed. */
  52         unsigned num_eq;        /**< Number of equalities placed. */
  53         unsigned num_non_null;  /**< Number of non-null Confirms. */
  54 } env_t;
  55
  56 /** The debug handle. */
  57 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
  58
  59 /**
  60  * Return the effective use block of a node and its predecessor on
  61  * position pos.
  62  *
  63  * @param node  the node
  64  * @param pos   the position of the used input
  65  *
  66  * This handles correctly Phi nodes.
  67  */
  68 static ir_node *get_effective_use_block(ir_node *node, int pos)
  69 {
  70         if (is_Phi(node)) {
  71                 /* the effective use of a Phi argument is in its predecessor block */
  72                 node = get_nodes_block(node);
  73                 return get_Block_cfgpred_block(node, pos);
  74         }
  75         return get_nodes_block(node);
  76 }
  77
  78 static ir_node *get_case_value(ir_node *switchn, long pn)
  79 {
  80         ir_graph              *irg       = get_irn_irg(switchn);
  81         const ir_switch_table *table     = get_Switch_table(switchn);
  82         size_t                 n_entries = ir_switch_table_get_n_entries(table);
  83         ir_tarval             *val       = NULL;
  84         size_t                 e;
  85         for (e = 0; e < n_entries; ++e) {
  86                 const ir_switch_table_entry *entry
  87                         = ir_switch_table_get_entry_const(table, e);
  88                 if (entry->pn != pn)
  89                         continue;
  90                 /* multiple matching entries gets too complicated for a single
  91                  * Confirm */
  92                 if (val != NULL)
  93                         return NULL;
  94                 /* case ranges are too complicated too */
  95                 if (entry->min != entry->max)
  96                         return NULL;
  97                 val = entry->min;
  98         }
  99         assert(val != NULL);
 100         return new_r_Const(irg, val);
 101 }
 102
 103 /**
 104  * Handle a CASE-branch.
 105  *
 106  * Branch labels are a simple case. We can replace the value
 107  * by a Const with the branch label.
 108  */
 109 static void handle_case(ir_node *block, ir_node *switchn, long pn, env_t *env)
 110 {
 111         ir_node         *c = NULL;
 112         ir_node         *selector = get_Switch_selector(switchn);
 113         const ir_edge_t *edge;
 114         const ir_edge_t *next;
 115
 116         /* we can't do usefull things with the default label */
 117         if (pn == pn_Switch_default)
 118                 return;
 119
 120         foreach_out_edge_safe(selector, edge, next) {
 121                 ir_node *succ = get_edge_src_irn(edge);
 122                 int     pos   = get_edge_src_pos(edge);
 123                 ir_node *blk  = get_effective_use_block(succ, pos);
 124
 125                 if (block_dominates(block, blk)) {
 126                         /*
 127                          * Ok, we found a user of irn that is placed
 128                          * in a block dominated by the branch block.
 129                          * We can replace the input with the Constant
 130                          * branch label.
 131                          */
 132                         if (c == NULL)
 133                                 c = get_case_value(switchn, pn);
 134
 135                         set_irn_n(succ, pos, c);
 136                         DBG_OPT_CONFIRM_C(selector, c);
 137                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 138
 139                         env->num_consts += 1;
 140                 }
 141         }
 142 }
 143
 144 /**
 145  * Handle a mode_b input of Cond nodes.
 146  *
 147  * @param block     the block which is entered by the branch
 148  * @param selector  the mode_b node expressing the branch condition
 149  * @param pnc       the true/false condition branch
 150  * @param env       statistical environment
 151  */
 152 static void handle_modeb(ir_node *block, ir_node *selector, pn_Cond pnc, env_t *env)
 153 {
 154         ir_node *cond, *old, *other_blk = NULL, *con = NULL;
 155         ir_node *c_b = NULL, *c_o = NULL;
 156         const ir_edge_t *edge, *next;
 157
 158         for (edge = get_irn_out_edge_first(selector); edge; edge = next) {
 159                 ir_node *user     = get_edge_src_irn(edge);
 160                 int     pos       = get_edge_src_pos(edge);
 161                 ir_node *user_blk = get_effective_use_block(user, pos);
 162
 163                 next = get_irn_out_edge_next(selector, edge);
 164                 if (block_dominates(block, user_blk)) {
 165                         /*
 166                          * Ok, we found a usage of selector in a block
 167                          * dominated by the branch block.
 168                          * We can replace the input with true/false.
 169                          */
 170                         if (con == NULL) {
 171                                 ir_graph *irg = get_irn_irg(block);
 172                                 con = new_r_Const(irg, pnc == pn_Cond_true ? tarval_b_true : tarval_b_false);
 173                         }
 174                         old = get_irn_n(user, pos);
 175                         set_irn_n(user, pos, con);
 176                         DBG_OPT_CONFIRM_C(old, con);
 177
 178                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, con));
 179
 180                         env->num_consts += 1;
 181                 } else {
 182                         int i, n;
 183
 184                         /* get the other block */
 185                         if (other_blk == NULL) {
 186                                 /* we have already tested, that block has only ONE Cond predecessor */
 187                                 cond = get_Proj_pred(get_Block_cfgpred(block, 0));
 188                                 foreach_out_edge(cond, edge) {
 189                                         ir_node *proj = get_edge_src_irn(edge);
 190                                         if (get_Proj_proj(proj) == (long)pnc)
 191                                                 continue;
 192                                         edge = get_irn_out_edge_first(proj);
 193                                         other_blk = get_edge_src_irn(edge);
 194                                         break;
 195                                 }
 196                                 assert(other_blk);
 197
 198                                 /*
 199                                  * Note the special case here: if block is a then, there might be no else
 200                                  * block. In that case the other_block is the user_blk itself and pred_block
 201                                  * is the cond_block ...
 202                                  *
 203                                  * Best would be to introduce a block here, removing this critical edge.
 204                                  * For some reasons I cannot repair dominance here, so I have to remove
 205                                  * ALL critical edges...
 206                                  * FIXME: This should not be needed if we could repair dominance ...
 207                                  */
 208                         }
 209
 210                         n = get_Block_n_cfgpreds(user_blk);
 211
 212                         /*
 213                          * We have found a user in a non-dominated block:
 214                          * check, if all its block predecessors are dominated.
 215                          * If yes, place a Phi.
 216                          */
 217                         for (i = n - 1; i >= 0; --i) {
 218                                 ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 219
 220                                 if (!block_dominates(block, pred_blk) &&
 221                                     !block_dominates(other_blk, pred_blk)) {
 222                                         /* can't do anything */
 223                                         break;
 224                                 }
 225                         }
 226                         if (i < 0) {
 227                                 ir_node *phi, **in;
 228
 229                                 NEW_ARR_A(ir_node *, in, n);
 230                                 /* ok, ALL predecessors are either dominated by block OR other block */
 231                                 if (c_b == NULL) {
 232                                         ir_graph *irg    = get_irn_irg(block);
 233                                         ir_node *c_true  = new_r_Const(irg, tarval_b_true);
 234                                         ir_node *c_false = new_r_Const(irg, tarval_b_false);
 235                                         env->num_consts += 2;
 236                                         if (pnc == pn_Cond_true) {
 237                                                 c_b = c_true;
 238                                                 c_o = c_false;
 239                                         } else {
 240                                                 c_b = c_false;
 241                                                 c_o = c_true;
 242                                         }
 243                                 }
 244                                 for (i = n - 1; i >= 0; --i) {
 245                                         ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 246
 247                                         if (block_dominates(block, pred_blk))
 248                                                 in[i] = c_b;
 249                                         else
 250                                                 in[i] = c_o;
 251                                 }
 252                                 phi = new_r_Phi(user_blk, n, in, mode_b);
 253                                 set_irn_n(user, pos, phi);
 254                                 env->num_eq += 1;
 255                         }
 256                 }
 257         }
 258 }
 259
 260 /**
 261  * Handle an IF-branch.
 262  *
 263  * @param block   the block which is entered by the branch
 264  * @param cmp     the Cmp node expressing the branch condition
 265  * @param rel     the Compare relation for taking this branch
 266  * @param env     statistical environment
 267  */
 268 static void handle_if(ir_node *block, ir_node *cmp, ir_relation rel, env_t *env)
 269 {
 270         ir_node *left  = get_Cmp_left(cmp);
 271         ir_node *right = get_Cmp_right(cmp);
 272         ir_node *cond_block;
 273         ir_op *op;
 274         const ir_edge_t *edge, *next;
 275
 276         /* Beware of Bads */
 277         if (is_Bad(left) || is_Bad(right))
 278                 return;
 279
 280         op = get_irn_op(left);
 281
 282         /* Do not create Confirm nodes for Cmp(Const, Const) constructs.
 283            These are removed anyway */
 284         if (op == op_Const && is_Const(right))
 285                 return;
 286
 287         /* try to place the constant on the right side for a Confirm */
 288         if (op == op_Const || op == op_SymConst) {
 289                 ir_node *t = left;
 290
 291                 left  = right;
 292                 right = t;
 293
 294                 rel = get_inversed_relation(rel);
 295         }
 296
 297         /*
 298          * First case: both values are identical.
 299          * replace the left one by the right (potentially const) one.
 300          */
 301         if (rel == ir_relation_equal) {
 302                 cond_block = get_Block_cfgpred_block(block, 0);
 303                 for (edge = get_irn_out_edge_first(left); edge; edge = next) {
 304                         ir_node *user = get_edge_src_irn(edge);
 305                         int     pos   = get_edge_src_pos(edge);
 306                         ir_node *blk  = get_effective_use_block(user, pos);
 307
 308                         next = get_irn_out_edge_next(left, edge);
 309                         if (block_dominates(block, blk)) {
 310                                 /*
 311                                  * Ok, we found a usage of left in a block
 312                                  * dominated by the branch block.
 313                                  * We can replace the input with right.
 314                                  */
 315                                 set_irn_n(user, pos, right);
 316                                 DBG_OPT_CONFIRM(left, right);
 317
 318                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, right));
 319
 320                                 env->num_eq += 1;
 321                         } else if (block_dominates(blk, cond_block)
 322                                         && is_Const(right)
 323                                         && get_irn_pinned(user) == op_pin_state_floats) {
 324                                 /*
 325                                  * left == Const and we found a movable user of left in a
 326                                  * dominator of the Cond block
 327                                  */
 328                                 const ir_edge_t *user_edge;
 329                                 const ir_edge_t *user_next;
 330                                 foreach_out_edge_safe(user, user_edge, user_next) {
 331                                         ir_node *usr_of_usr = get_edge_src_irn(user_edge);
 332                                         int      npos       = get_edge_src_pos(user_edge);
 333                                         ir_node *user_blk   = get_effective_use_block(usr_of_usr, npos);
 334
 335                                         if (block_dominates(block, user_blk)) {
 336                                                 /*
 337                                                  * The user of the user is dominated by our true/false
 338                                                  * block. So, create a copy of user WITH the constant
 339                                                  * replacing its pos'th input.
 340                                                  *
 341                                                  * This is always good for unop's and might be good
 342                                                  * for binops.
 343                                                  *
 344                                                  * If user has other user in the false/true block, code
 345                                                  * placement will move it down.
 346                                                  * If there are users in cond block or upper, we create
 347                                                  * "redundant ops", because one will have a const op,
 348                                                  * the other no const ...
 349                                                  */
 350                                                 ir_node *new_op = exact_copy(user);
 351                                                 set_nodes_block(new_op, block);
 352                                                 set_irn_n(new_op, pos, right);
 353                                                 set_irn_n(usr_of_usr, npos, new_op);
 354                                                 env->num_eq += 1;
 355                                         }
 356                                 }
 357                         }
 358                 }
 359         } else { /* not ir_relation_equal cases */
 360                 ir_node *c = NULL;
 361
 362                 foreach_out_edge_safe(left, edge, next) {
 363                         ir_node *succ = get_edge_src_irn(edge);
 364                         int     pos   = get_edge_src_pos(edge);
 365                         ir_node *blk  = get_effective_use_block(succ, pos);
 366
 367                         if (block_dominates(block, blk)) {
 368                                 /*
 369                                  * Ok, we found a usage of left in a block
 370                                  * dominated by the branch block.
 371                                  * We can replace the input with a Confirm(left, pnc, right).
 372                                  */
 373                                 if (! c)
 374                                         c = new_r_Confirm(block, left, right, rel);
 375
 376                                 pos = get_edge_src_pos(edge);
 377                                 set_irn_n(succ, pos, c);
 378                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 379
 380                                 env->num_confirms += 1;
 381                         }
 382                 }
 383
 384                 if (! is_Const(right)) {
 385                         /* also construct inverse Confirms */
 386                         ir_node *rc = NULL;
 387
 388                         rel = get_inversed_relation(rel);
 389                         foreach_out_edge_safe(right, edge, next) {
 390                                 ir_node *succ = get_edge_src_irn(edge);
 391                                 int     pos;
 392                                 ir_node *blk;
 393
 394                                 if (succ == c)
 395                                         continue;
 396
 397                                 pos  = get_edge_src_pos(edge);
 398                                 blk  = get_effective_use_block(succ, pos);
 399
 400                                 if (block_dominates(block, blk)) {
 401                                         /*
 402                                          * Ok, we found a usage of right in a block
 403                                          * dominated by the branch block.
 404                                          * We can replace the input with a Confirm(right, rel^-1, left).
 405                                          */
 406                                         if (! rc)
 407                                                 rc = new_r_Confirm(block, right, left, rel);
 408
 409                                         pos = get_edge_src_pos(edge);
 410                                         set_irn_n(succ, pos, rc);
 411                                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, rc));
 412
 413                                         env->num_confirms += 1;
 414                                 }
 415                         }
 416                 }
 417         }
 418 }
 419
 420 /**
 421  * Pre-block-walker: Called for every block to insert Confirm nodes
 422  */
 423 static void insert_Confirm_in_block(ir_node *block, void *data)
 424 {
 425         env_t   *env = (env_t*) data;
 426         ir_node *cond;
 427         ir_node *proj;
 428
 429         /*
 430          * we can only handle blocks with only ONE control flow
 431          * predecessor yet.
 432          */
 433         if (get_Block_n_cfgpreds(block) != 1)
 434                 return;
 435
 436         proj = get_Block_cfgpred(block, 0);
 437         if (! is_Proj(proj))
 438                 return;
 439
 440         cond = get_Proj_pred(proj);
 441         if (is_Switch(cond)) {
 442                 long proj_nr = get_Proj_proj(proj);
 443                 handle_case(block, cond, proj_nr, env);
 444         } else if (is_Cond(cond)) {
 445                 ir_node *selector = get_Cond_selector(cond);
 446                 ir_relation rel;
 447
 448                 handle_modeb(block, selector, (pn_Cond) get_Proj_proj(proj), env);
 449
 450                 if (! is_Cmp(selector))
 451                         return;
 452
 453                 rel = get_Cmp_relation(selector);
 454
 455                 if (get_Proj_proj(proj) != pn_Cond_true) {
 456                         /* it's the false branch */
 457                         rel = get_negated_relation(rel);
 458                 }
 459                 DB((dbg, LEVEL_2, "At %+F using %+F Confirm %=\n", block, selector, rel));
 460
 461                 handle_if(block, selector, rel, env);
 462         }
 463 }
 464
 465 /**
 466  * Checks if a node is a non-null Confirm.
 467  */
 468 static int is_non_null_Confirm(const ir_node *ptr)
 469 {
 470         for (;;) {
 471                 if (! is_Confirm(ptr))
 472                         break;
 473                 if (get_Confirm_relation(ptr) == ir_relation_less_greater) {
 474                         ir_node *bound = get_Confirm_bound(ptr);
 475
 476                         if (is_Const(bound) && is_Const_null(bound))
 477                                 return 1;
 478                 }
 479                 ptr = get_Confirm_value(ptr);
 480         }
 481         /*
 482          * While a SymConst is not a Confirm, it is non-null
 483          * anyway. This helps to reduce the number of
 484          * constructed Confirms.
 485          */
 486         if (is_SymConst_addr_ent(ptr))
 487                 return 1;
 488         return 0;
 489 }
 490
 491 /**
 492  * The given pointer will be dereferenced, add non-null Confirms.
 493  *
 494  * @param ptr    a node representing an address
 495  * @param block  the block of the dereferencing instruction
 496  * @param env    environment
 497  */
 498 static void insert_non_null(ir_node *ptr, ir_node *block, env_t *env)
 499 {
 500         const ir_edge_t *edge, *next;
 501         ir_node         *c = NULL;
 502
 503         foreach_out_edge_safe(ptr, edge, next) {
 504                 ir_node *succ = get_edge_src_irn(edge);
 505                 int     pos;
 506                 ir_node *blk;
 507
 508
 509                 /* for now, we place a Confirm only in front of a Cmp */
 510                 if (! is_Cmp(succ))
 511                         continue;
 512
 513                 pos = get_edge_src_pos(edge);
 514                 blk = get_effective_use_block(succ, pos);
 515
 516                 if (block_dominates(block, blk)) {
 517                         /*
 518                          * Ok, we found a usage of ptr in a block
 519                          * dominated by the Load/Store block.
 520                          * We can replace the input with a Confirm(ptr, !=, NULL).
 521                          */
 522                         if (c == NULL) {
 523                                 ir_mode  *mode = get_irn_mode(ptr);
 524                                 ir_graph *irg  = get_irn_irg(block);
 525                                 c = new_r_Const(irg, get_mode_null(mode));
 526                                 c = new_r_Confirm(block, ptr, c, ir_relation_less_greater);
 527                         }
 528
 529                         set_irn_n(succ, pos, c);
 530                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 531
 532                         env->num_non_null += 1;
 533                         env->num_confirms += 1;
 534                 }
 535         }
 536 }
 537
 538 /**
 539  * Pre-walker: Called for every node to insert Confirm nodes
 540  */
 541 static void insert_Confirm(ir_node *node, void *data)
 542 {
 543         ir_node *ptr;
 544         env_t   *env = (env_t*) data;
 545
 546         switch (get_irn_opcode(node)) {
 547         case iro_Block:
 548                 insert_Confirm_in_block(node, env);
 549                 break;
 550         case iro_Load:
 551                 ptr = get_Load_ptr(node);
 552                 if (! is_non_null_Confirm(ptr))
 553                         insert_non_null(ptr, get_nodes_block(node), env);
 554                 break;
 555         case iro_Store:
 556                 ptr = get_Store_ptr(node);
 557                 if (! is_non_null_Confirm(ptr))
 558                         insert_non_null(ptr, get_nodes_block(node), env);
 559                 break;
 560         default:
 561                 break;
 562         }
 563 }
 564
 565 void construct_confirms(ir_graph *irg)
 566 {
 567         env_t env;
 568         FIRM_DBG_REGISTER(dbg, "firm.ana.confirm");
 569
 570         assure_irg_properties(irg,
 571               IR_GRAPH_PROPERTY_CONSISTENT_OUT_EDGES
 572                 | IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE
 573                 | IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES);
 574
 575         assert(get_irg_pinned(irg) == op_pin_state_pinned &&
 576                "Nodes must be placed to insert Confirms");
 577
 578         env.num_confirms = 0;
 579         env.num_consts   = 0;
 580         env.num_eq       = 0;
 581         env.num_non_null = 0;
 582
 583         if (get_opt_global_null_ptr_elimination()) {
 584                 /* do global NULL test elimination */
 585                 irg_walk_graph(irg, insert_Confirm, NULL, &env);
 586         } else {
 587                 /* now, visit all blocks and add Confirms where possible */
 588                 irg_block_walk_graph(irg, insert_Confirm_in_block, NULL, &env);
 589         }
 590
 591         DB((dbg, LEVEL_1, "# Confirms inserted : %u\n", env.num_confirms));
 592         DB((dbg, LEVEL_1, "# Const replacements: %u\n", env.num_consts));
 593         DB((dbg, LEVEL_1, "# node equalities   : %u\n", env.num_eq));
 594         DB((dbg, LEVEL_1, "# non-null Confirms : %u\n", env.num_non_null));
 595
 596         confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_CONTROL_FLOW);
 597 }
 598
 599 ir_graph_pass_t *construct_confirms_pass(const char *name)
 600 {
 601         return def_graph_pass(name ? name : "confirm", construct_confirms);
 602 }
 603
 604 static void remove_confirm(ir_node *n, void *env)
 605 {
 606         ir_node *value;
 607
 608         (void) env;
 609         if (!is_Confirm(n))
 610                 return;
 611
 612         value = get_Confirm_value(n);
 613         exchange(n, value);
 614 }
 615
 616 void remove_confirms(ir_graph *irg)
 617 {
 618         irg_walk_graph(irg, NULL, remove_confirm, NULL);
 619         confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_CONTROL_FLOW);
 620 }
 621
 622 ir_graph_pass_t *remove_confirms_pass(const char *name)
 623 {
 624         return def_graph_pass(name ? name : "rem_confirm", remove_confirms);
 625 }